The present invention relates to a sealing device for shafts passing through the wall or housing of a machine part containing a liquid or gaseous (vapor) medium under a pressure differing from that of the environment. A common type of sealing device is the stuffing box, forming around the shaft an annular chamber in which packing strips, in the form of braid for example, are applied in rings around the shaft. These strips are pressed against the shaft by a nut or gland that closes the chamber at the side. The pressure on the packing strips is very unevenly distributed inasmuch as it is concentrated on that part of the packing strips nearest the gland, the rest of the strips being loose on the shaft. The narrow section of the packing braid subjected to the severest stress wears relatively fast, with the result that escape of the medium through the stuffing box increases rapidly, requiring repeated repositioning of the gland. In practice it is difficult to carry out these adjustments at the frequent intervals that are desirable. The purpose of the invention is the elimination of these drawbacks, which is essentially achieved by mounting around the layer of packing a sleeve which is flexible in the radial direction, and preferably made of elastic material and which on its radially exterior side is subjected to pressure through a medium, this pressure being transmitted radially inward through the sleeve to the packing layer.
The invention automatically brings about the even distribution of the pressure of the packing against the shaft along the entire length of the chamber. This pressure may be adjusted so as to prevent or minimize the leakage along the shaft.